I would highly recommend using a controller card or using a built in RAID controller on the motherboard. Trust me, you don't want Windows managing more important things than it needs to. I forsee huge headaches in the future if Windows ever gets corrupted. And being quite the techy myself, I've seen too many bad things happen with windows like that. Do yourself a favor and get a controller card, have that manage it, and have Windows think it's just operating on a single hard drive.
It's going to be a nightmarish experience if Windows does go bad, and all/any of your data is innacessable. With a hardware controller, you don't have to worry about that.
I'm not entirely sure if the system will recognize the drives as a RAID5 again if you need to reinstall. That's a lot of data there.
